Overspeed governor



NOV. 10, 1931. 511-11 v 1,830,891

OVERS'PEED GOVERNOR Filed April 17, 1930 WITNESS I I INVENTOR KarlSillig.

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ATTORNEY Patented Nov. 10, 1931 UNITED STATES [PATENT OFFICE KARLSITTIG, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELEC-TRIO & MANUFACTURING COMPANY,

A CORPORATION OF PENNSYLVANIA OVERSPEED GOVERNOR Application filed April17,

other governing device is an overspeed gov-' ernor, which guards againsta dangerous overspeed in case of failure of the regulating governor orother speed-limiting means. Itoperates at a predetermined overspeed ofabout above the normal operating speed, acting on a separatequick-closing throttle valve to effect complete closing movement thereofand preferably embodies a trip mechanismwhich must be reset before thethrottle valve can be reopened.

Inasmuch as the tripping macha-nism must be reset before operation ofthe prime mover can be resumed, it is desirable to control the admissionvalve so as to maintain the speed below the predetermined overspeed,thereby avoiding operation of the overspeed governor.

In accordance with my invention, I provide an overspeed governorcomprising an element movable in accordance with the speed 7 of theprime mover, and I also provide means which is effective upon movementof said element in response to an overspeed above the governlng range ofthe regulating governor but below the usual overspeed at which i thethrottle valve is tripped, and operatesto effect closing of theadmission valve normally controlled by the regulating governor. Stillfurther means are provided for tripping the throttle valve upon movementof the element in response to speed of the prime mover above the usualoverspeed of about 10%. The above and other objects are effected bv myinvention as will be apparent from the following description and claimstaken in connection with the accompanying drawing,

.sure when starting the prime mover.

1930. Serial No. 445,233.

forming a part of this application, inwhich:

The single figure is a diagrammatic view of the governing mechanism, theo-verspeed governor being shown in section on an enlarged scale.Referring now to the drawing more in detail, I show an elastic fluidturbine 10 supplied with motive fluid through a conduit 11. The'motivefluid first passes through a throttle valve 12, which is fully open inthe normal operation of the prime mover, and thence through an admissionvalve 13, which regulates the motive fluid admissionin response to thespeed or other operating condition of the prime mover.

The admission valve 13 is operated by any suitable regulating mechanismknown in the art. For example, a fluid pressure governor 14 is shown,which may be of the type described and claimed in the patent of H. F.Schmidt, No. 1,533,7 67, issued April 14, 1925. The governor 14 includesa fluid actuated operating piston41, constituting part of a fluidpressure relay and connected to the admission valve 13 through a lever15 fulcrumed at 16. A, spring 17 acts 011 the lever 15in the directionfor closing the admission valve 13.

The throttle valve 12 is operated by a piston 18 disposed in a cylinder19 and to which it is connected by a rod 21. The piston 18 is biased inthe direction for closing the throttle valve 12 by a spring 22, and apassage through the piston 18 is provided at 23. A screw threaded stem24 extends through the upper end wall of the cylinder 19 and is adaptedto close the upper endof the passage 23. A hand wheel 25 is fastened onthe stem 24 for operating the same.

To provide fluid pressure varying as the square of the speed of theturbine 10, I provide a pump including an impeller 26 mounted directlyon the, turbine shaft 27 and discharging into a conduit 28. An auxiliarypump 29, arranged to discharge into the conduit 28, is also providedtosupply fluid pres- Check valves 31 and 32 are provided to prevent flowfrom either pump to the other. t The overspeed governor may be housed ina structure unitary with the cylinder 19, and

in the present embodiment it includes a cylindrical chamber 33 formed bythe cylinder structure. A passage 34 communicating with the lower end ofthe cylinder 19 is also provided and communicates with an annular recess35 in the cylindrical chamber 33. The conduit 28 communicates with thelower end of the chamber 33, and a restricted orifice36provides-arestricted flow of fluid through the passage 34 to the lowerendof the cylinder 19.

The chamber 33 is also provided with an annular recess 37 communicatingthrough a conduit 38 with any suitable mechanism for effecting-completeclosing of the admission valve 13. This mechanism may include a valve39, which is adapted to release fluid pressure from that side of theoperatingpiston 41 embodied in the governor'14 on which fluid pressureacts on the operating piston to move theadmis'sion valve 13 in openingdirection, thereby rendering the spring 17 effective to" close theadmission valve 13.

The valve 39 is operated by a piston 42, biased in the direction foropening the valve 39 by aspring 43. A restricted flow of fluid from theconduit 28 into the conduit 38 is provided through a conduit 44containing a restricted orifice 4'5, and the fluid pressure in theconduit 38 normally acts on the piston 4 2'to close the valve 39,permitting operation of the admission valve 13 by the governor 14 inresponse to the speed of the prime mover.

The chamber 33 is further provided with fluid discharge recesses 46 and47, communieating with a drain conduit 47 The upper end of the chamber33 communicates with the inlet of the pump 26 through a conduit 48.

Disposed within the chamber 33 is a' pilot valve 49, biased upwardly bythe impeller pressure in the lower end of the chamber 33 and downwardlyby a spring 51 connected at its lower end to a spring holding member 52.The latter is adapted to be adjusted to change the setting of the spring51 by a stem '53, on which the member 52 is screw threaded. The pilotvalve 49 is also biased downwardly by the pump inlet pressure, in orderto negative the variations in the pump discharge pressure caused byvariations in the pump inlet pressure.

The pilot valve 49 is formed with annular recesses 54 and 55. lVhen-theprime mover is operating at the desired normal operating speed, thepilot valve is disposed with the recesses in the position shown. In th1s'posltion, the recess 54 communicates with the annular row of ports 37,and the recess 55 communicates with the annular recess 35. The upperedge of the recess 54 is spaced by a small amount from the lower edge ofthe recess 47, so that as the pilot valve 49 moves upwardly, the recess54 places the recess 37 in communication with the recess 47. The uploweredge of the recess 46 by a greater amount, so that upon a still greaterupward movement of the pilot valve 49, the recess 55 places the recesses35 and 46 in communication.

A manually operated valve 56, controlling the discharge of fluid fromthe lower end of the cylinder 19 to a drain conduit 57, may alsobeprovided.

The operation of the above-described apparatus is as follows: i

Innormal operation, the throttle valve 12 is maintained in fully openedposition by the piston 18, which'is held at the upper end of its travelby fluid pressure developed by the impeller 26. The admission valve 13is controlled by the governor 14 to regulate the admission or motivefluidto the turbine 10.

The governor maintains the speed within a predetermined range, themaximum speed of which may be, for example, 4% above normal operatingspeed. The pilot valve 49 is in the position shown on the'drawing,cutting off the escape of fluid from the passage 34 and from the conduit38. The pressure in. the latter maintains the valve 39 closed,permitting the piston 41 of the governor to be actuated to operate theadmission valve 13.

In case of failure of the governor 14 to restrict the speed of theturbine, the fluid pressure developed by the pump 26 increases and movesthe pilot valve 49 upwardly by an amount proportional to the increase influid pressure. At a' predetermined 0verspeed which is above the maximumspeed provided by the governor 14 and below the overspeed at which thethrottle valve 12 is closed, for example, 6% above normal operatingspeed, the pilot valve 49 is brought to position placing the recesses 54and 47 in communication. The fluid pressure in the conduit 38 isreleased, and the spring moves the piston 42 downwardly. The valve 39 isopened, releasing fluid pressure from above the operating piston 41. Thespring 17 is thereupon efl'ective to move the valve 13 to closedposition, in' an'end e'avor to check further increase in speed.

Should this action prove inadequate to restrict increase in speed, andthe speed be increased by more than 10% above the normal operatingspeed, the pilot valve 49 moves upwardly to place the recess 55 incommunication with the recess 46. The fluid pressure in the lower end ofthe cylinder 19 is thereupon released through the passage 34, and thespring 22 acts on the'piston 18 to move the throttle valve to closedposition. The admission of motive fluid is now out ofl at a secondpoint, and cannot be restored until the throttle valve operatingmechanism is reset.

WVhen the turbine slows down again and the escape of fluid from thepassage 34 is per edge of the recess 55 is spaced from the out 01f atthe recess 46, the fluid escapes through the passage 23, the upper endof which has been opened by movement away from the stem 24. To reopenthe throttle valve, it is necessary to lower the stem 24; by rotation ofthe hand wheel 25 until it abuts the piston 18 and closes the passage28. The

throttle valve may then again be opened by slowly raising the stem 24,permitting the fluid pressure to raise the piston 18.

The purpose of interposing the valve 39 is to immediately provide ampledischarge area. As the recesses 54 and 47 come into communication, aslight discharge opening provided by the recesses is sufficient torelease the pressure of the fluid in the conduit 38, whereupon the valve39 provides ample discharge opening to release the fluid pressure abovethe piston 11.

By manually opening the valve 56, the throttle valve may be trippedclosed inde pendently of the action of the overspeed governor.

The advantage of the above construction is that a separate control isprovided. for effecting complete closing of the admission valve when thespeed begins to increase above the normal range. If closing of theadmission valve 13 is suflicient to restrict the speed below the 10%overspeed, operation of the throttle valve is avoided, and, upon returnto normal speed, admission of motive fluid to the turbine is restoredwithout the neoessity of resetting the throttle valve operatingmechanism.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various changes and modifications without departing from the spiritof my invention, and I desire, therefore, that only such limitationsshall be placed thereupon as are imposed by the prior art or as arespecifically set forth in the appended claims.

What I claim is:

1. The combination with a prime mover havin an admission valve and aquick-closing throttle valve, of a governing system therefor comprisingmeans for regulating the admission valve in accordance with a variableoperating condition of the prime mover, and emergency governor meansresponsive to an operating condition of the prime mover and operative toeffect closing of the admission valve upon a predetermined departure ofsaid last-mentioned operating condition from normal and to effectclosing of the throttle valve upon a predetermined departure from normalgreater than the first-mentioned departure.

2. The combination with a prime mover having an admission valve and aquick-closing throttle valve, of a governing system therefor comprisingmeans for regulating the admission valve in accordance with a variableoperating condition of the prime mover, and

an overspeed governor operative to effect closing of the admission valveupon a predetermined overspeed and to eflect closing of the throttle.valve upon a predetermined overspeed greater than the first-mentionedoverspeed.

3. The combination with a prime mover having an admission valve and aquick-closing throttle valve, of a governing system therefor comprisinga governor responsive to the speed of the prime mover for regulating theadmission valve, and an overspeed governor operative to eifectclosing ofthe admission valve upon a predetermined overspeed and to effect closingof the throttle valve upon a predetermined overspeed greater than thefirst-mentioned overspeed.

4. The combination with a prime mover having an admission valve and aquick-closing throttle valve, of a governing system thereforcomprising'a governor responsive to the speed of the prime mover forregulating the admission valve, and an overspeed governor operative toeffect closing of the admission valve upon a predetermined speed abovethe governing range of the first-mentioned governor and to effectclosing of the throttle valve upon a predetermined overspeed greaterthan said predetermined speed.

5. The combination with a prime mover having an admission valve and aquick-closing throttle valve, of a governing system therefor comprisinga governor responsive to an operating condition of the prime mover forregulating the admission valve, means providing a fluid pressure varyingas the speed of the prime mover, and an overspeed governor comprising anelement movable in response to said fluid pressure, means responsive tolimited movement of said element to effect closing of the admissionvalve, and means responsive to further movement of said element foreffecting closing of the throttle valve. s

6. The combination with a prime mover having an admission valve and aquick-closing throttle valve, of a governing system therefor comprisinga governor responsive to the speed of the prime mover for regulating theadmission valve, means providing a fluid pressure varying as the speedof vthe prime mover, and an overspeed governor comprising an elementmovable in response to said fluid pressure, means responsive to limitedtherefor comprising means for regulating the admission valve in responseto the speed of the prime mover, means providing a fluid pressurevarying as a fllIlCtlOl'l'Of the speed of the prime mover, and anoverspeedi governor coniprisingan element responsive to said fluidpressure an da spring biasingsaid element for determining the positionthereof in accord- "anee Wlilllijh' varying fluid pressure, meansresponsive to a position of said eleinent correspondingto apredetermined overspeed above the governing range of the governor forefiect-ingclosing of'tlie' admission valve, and 30 means responsive toaposition of said element correspondingto-an overspeed greaterthan'tliefirst-1nenti0ned overspeed for effecting closing of thethrottle valve.

In testimonywhere'of, I-have hereunto sub- 13 scribed niy name thissecond day of April,

KARL S-ITTIG;

